Direction controllable lighting units are known and used e.g. in lighting for entertainment purposes, such as in nightclubs and theatres. In the present context, the term “direction controllable” will be used to refer to lighting units which have a directed light emission, i.e. that has a specific direction as opposed to isotropic light emission (e.g. spot lights), where the direction of this light emission is automatically (non-manually) controllable, e.g. by a motorized movement of a lamp body comprising at least one light source, which results in a change of direction of the light emission.
WO 99/55122 relates to a lighting system including robotic lamps which may be remotely controlled by commands according to the DMX standard. In this way, parameters of a direction controllable lamp, such as coordinates for the X, Y and Z axes, pitch, yaw and roll angles may be controlled. The lamps orientation is sensed by sensors, e.g. pan/tilt motors may be equipped with shaft encoders which yield digital outputs of the actual pan/tilt angles. This allows for closed-loop control of the light emission direction, which may be used for 3D positioning tasks in real time.